1. Field
One embodiment of the present invention generally relates to a disk drive and particularly to a method and apparatus for writing servo data in a disk drive, by using spiral servo patterns.
2. Description of the Related Art
In most disk drives, a representative example of which is a hard disk drive, the positioning of the heads is controlled in accordance with the serve data (servo pattern) that is recorded on disk-shaped media, i.e., data-recording media. That is, the heads are moved to target positions (i.e., target tracks) on the disk-shaped media, in accordance with the servo data the heads have read.
The servo data recorded on any disk medium provided in a disk drive is recorded in servo sectors that are arranged at regular intervals in the circumferential direction of the disk medium. The servo sectors constitute concentric servo tracks. In the disk drive, a head is moved to a position over the disk medium, in accordance with the servo data. The head thus positioned records data on the disk medium, forming concentric data tracks.
The servo data is recorded on the disk medium in the servo-writing step included in the manufacture of the disk drive. A method of recording spiral servo patterns (hereinafter referred to as spiral servo patterns), i.e., base pattern, on a disk medium in the servo-writing step has been proposed (see, for example, U.S. Pat. No. 6,987,646B1 and U.S. Pat. No. 5,668,679).
In this method, a servo pattern (hereinafter called target servo pattern, for convenience), which will be used as a product servo pattern, is written on the disk medium. The target servo pattern is servo data that constitutes the above-mentioned concentric servo tracks. The disk drive to be shipped as product incorporates disk-shaped media, on each of which a target servo pattern is recorded.
In the method of writing servo data, described above, the density of the concentric servo tracks constituted by the target servo pattern is determined from the slope of the spiral servo patterns, after the target servo pattern has been written. Hence, the density of the concentric servo tracks changes as the slope of the spiral servo patterns changes.